Traditionally, the multiple components required to build a pneumatic tire are assembled on a tire building drum rotatably mounted in front of the operator. The components are presented from individual servers or component racks located on the side of the assembly drum opposite the operator or adjacent to him. The operator then rotates the drum and by the use of mechanical aids guides the successive components into their proper position on the assembly drum.
This has been the traditional method and apparatus for making bias ply tires. However, radial tires require very precise placement of the various components and, for production runs, the ability to repeat accurately the placement of components.
It should be appreciated that whereas bias ply tires can be assembled in their entirety as a cylindrical band and then shaped and cured in a mold, the casing for a radial tire must generally be shaped to its toroidal configuration prior to placement of the inextensible bands that underlie the treadstock. Hence, radial tires are often built by a two-stage process. That is, the components, except for the belts and treadstock, are assembled on a first drum, the beads are set in place and the resulting cylindrical band removed and mounted on a second drum which expands the band into a toroidal casing, whereupon the belts and treadstock are applied. This much handling can be deleterious unless extreme caution is exercised.
It is, therefore, desirable to build the entire tire on a single-stage drum so that the green tire is completed before removal. It has, however, heretofore been difficult to achieve accurate bead placement and accurate belt placement on the same drum, largely because of the multiplicity of servers required at a single location and the multiple guides required to place components on a cylindrical surface and later components on a toroidal surface at the same location, while relating placement of all components to a single reference plane transversely of the rotational axis of the finished product.